Fungi are simple life forms such as molds, mildews, yeasts and mushrooms, with over 100,000 different species of fungi known to exist worldwide. Although most fungi are harmless, there a number of species that can cause illness and even fatal disease. The study of fungi and fungal diseases is referred to as mycology.
Fungi can cause various diseases and infections such as pulmonary candidiasis and blastomycosis. certain yeastlike organisms, e.g., Cryptococcus neoformans, may cause serious infections of the central nervous system. These fungal diseases are classified as "deep" fungal infections, which are those affecting the internal organs. Fungal infections may also be classified as superficial, which encompasses those affecting the skin, hair, nails, and genitals. Common superficial fungal infections include candidiasis (thrush), caused by the yeast Candida albicans, and tinea (including ringworm and athletes foot).
The incidence of opportunistic fungal infections in humans has steadily increased over the past several years. This is particularly true among patients whose immune systems have been compromised by conditions such as hematologic malignancy, myelosuppressive therapy, or HIV infection.
Fungal infections caused by Candida and Torulopsis have been reported in nearly 12 percent of leukemia patients following chemotherapy. Acute candidiasis has is currently on the rise, infecting up to five percent of newborns, five percent of all cancer patients, and ten percent of debilitated, elderly hospital patients. Candida albicans has become the fourth most common causal agent of sepsis in the United States, with a five-fold increased incidence during the decade of the 1980's, and mortality rates of 50 to 90 percent. The Centers for Disease Control (CDC) estimate that between 3 and 25 percent of patients with AIDS or AIDS related complex (ARC) will develop an opportunistic disease, with Cryptococcus neoformans constituting the fourth most common infection in these patients. Overall, over 30 percent of reported AIDS patients have had associated, potentially fatal, mycotic infections.
The incidence of non-albicans candidiasis, such as C. kruzii and C. glabrata is also increasing, possibly due to the emergence of organisms that are resistant to current antifungal therapies. Infections caused by species of Aspergillus, Fusarium, and Trichosporon, each associated with high mortality rates, are also increasing. Additionally, fungal species previously believed to be benign are beginning to appear as agents of previously unrecognized mycoses.
Even with the increase in the incidence of serious fungal infections, the number of current therapies available to counter these mycoses has been rather limited. Amphotericin B, developed in the 1950's, still remains the drug of choice for most fungal diseases, even though its toxicity causes undesirable side-effects including leucopenia, thrombocytopenia, renal tubular acidosis, hypokalemia, hypomagnesemia, headaches, nausea, and anemia (Thomas, 1986). Thus, a need exists for new antifungal compounds which are safe and effective in the treatment of fungal diseases.
Plants are also attacked by various fungi. Detrimental fungal plant pathogens include Fusarium oxysporum, which causes wilt in numerous plants, Sclerotinia sclerotiorum, which causes scelerotinia wilt, and Rhizoctonia solani, which can cause seedling damping off and root rot disease. Although most crops are treated with agricultural fungistats or fungicides, fungal damage to agricultural crops typically results in revenue losses to the agricultural industry of millions of dollars annually.
Pseudomonas viridiflava is a phytopathogenic bacterium associated with foliar, bud, flower, fruit, stem, or root diseases in a variety of plant species. Strains that are capable of producing necrotic and cankerlike lesions in plants have also been identified. Surprisingly, it has been discovered that certain novel lipopeptide compounds produced by Pseudomonas viridiflava possess potent antifungal properties.